Present methods of patterning magnetic films consist of chemical etching, ion milling, and sputter etching. Some of the processes require precise control of both the etching time and the bias voltages to ensure complete removal of the magnetic material. Some applications where it is desirable to pattern magnetic films or to delineate magnetic circuits is for track formation in magnetic storage media, inductive heads for reading and writing into magnetic storage media, and magneto resistive heads for reading magnetic storage media. The formation of tracks of magnetic storage media eases the problem of head registration on the magnetic storage media and permits high density, data storage.
Recording tracks of magnetic storage media have been formed in the past by electrodepositing media through photoresist masks.
In a publication by C. H. Bajorek et al. entitled, "Magnetically discrete but physically continuous recording tracks", IBM Technical Disclosure Bulletin, Vol. 18. No. 5, pp. 1641 (1975), a process was described for forming discrete tracks of magnetic storage media from nonmagnetic amorphous Fe.sub.2 O.sub.3 or Fe.sub.x Co.sub.y O.sub.3 which may be deposited by sputtering, evaporation, or chemical vapor deposition. The layer may have a thickness of 1000 .ANG. and have a pattern thereover of photoresist corresponding to the desired tracks. Next, a thin film of FeCo or Fe, Co is evaporated or sputtered to form a layer over the photoresist and the nonmagnetic film. A suitable resist solvent is used to lift the metal in unwanted areas while removing the resist. The residual structure is annealed to diffuse the Fe, Co or Fe-Co into the nonmagnetic layer and thus transform the nonmagnetic layer to a ferromagnetic Fe.sub.3 O.sub.4 or Fe.sub.x Co.sub.y O.sub.4. Metals not diffused into the layer are subsequently removed to form a uniform layer thickness of ferromagnetic tracks with nonmagnetic material therebetween.
Another approach for forming discrete tracks for a magnetic recording disk was described in U.S. Pat. No. 4,935,278 which issued on Jun. 19, 1990 to Krounbi et al. entitled, "Thin film magnetic recording disk and fabrication process" and assigned to the assignee herein. A thin film of magnetic material is formed on a substrate, patterned by sputter etching with a chemically etchable support layer and a high resolution photoresist layer. The removed portions of magnetic film are refilled with nonmagnetic material preferably by sputter deposition to form concentric nonmagnetic guard bands. The original magnetic film layer may be a magnetic cobalt-based alloy which may be sputter deposited to a thickness of approximately 300 .ANG.. The substrate or disk may comprise an aluminum alloy disk with a surface film of nickel-phosphorous. The recording tracks of magnetic film and the nonmagnetic material therebetween may be covered by a top layer of nonmagnetic material which functions as a passivating and protective disk overcoat.
A further example of patterning magnetic films is described in U.S. Pat. No. 4,746,580 which issued on May 24, 1988 to R. W. Bishop ct al. entitled, "Read-only magnetic recording media" which is assigned to the assignee herein. In '580, discrete bits of high coercivity metal are formed by patterning resist on a substrate, depositing high coercivity metal, for example, an alloy of aluminum, nickel, and cobalt. The photoresist is chemically removed lifting off the metal over the resist leaving a defined pattern of discrete bits on the substrate. The substrate may be a thin nonmagnetic stainless steel about 0.002 inches thick or a polyester film. The discrete bits or metal islands are subjected to the influence of a steady-state magnetic field in order to convert the metal islands into a read-only data pattern which can be read by a magnetic head.
Outside the prior art of magnetic thin films but within the art or storage media, information can be stored in a suitable storage media by exposure to a focussed laser beam. In U.S. Pat. No. 3,959,799 which issued on May 25, 1976 to R. J. Gambino et al., entitled, "Information storage by laser beam initiated reaction", a storage media was provided initially comprising two adjacent thin layers of two or more materials which react upon heating to form a reaction product with optical, magnetic, or electrical properties different from the corresponding properties of the reactive materials. One example of a storage media is a layer of aluminum adjacent a layer of selenium. A laser may be focussed on selected areas of the layers wherein the heating clue to the laser results in a reaction product of Al.sub.2 Se.sub.3. The storage media provides a relatively low cost read-only memory after information has been stored therein with a laser.